On Fri, Apr 22, 2022 at 10:47:32AM +0800, Miaohe Lin wrote:
> On 2022/4/21 22:28, Peter Xu wrote:
> > On Thu, Apr 21, 2022 at 08:53:48PM +0800, Miaohe Lin wrote:
> >> Once the MADV_FREE operation has succeeded, callers can expect they might
> >> get zero-fill pages if accessing the memory again. Therefore it should be
> >> safe to delete the hwpoison entry and swapin error entry. There is no
> >> reason to kill the process if it has called MADV_FREE on the range.
> >>
> >> Suggested-by: Alistair Popple <apopple@xxxxxxxxxx>
> >> Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
> >> ---
> >> mm/madvise.c | 13 ++++++++-----
> >> 1 file changed, 8 insertions(+), 5 deletions(-)
> >>
> >> diff --git a/mm/madvise.c b/mm/madvise.c
> >> index 4d6592488b51..5f4537511532 100644
> >> --- a/mm/madvise.c
> >> +++ b/mm/madvise.c
> >> @@ -624,11 +624,14 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
> >> swp_entry_t entry;
> >>
> >> entry = pte_to_swp_entry(ptent);
> >> - if (non_swap_entry(entry))
> >> - continue;
> >> - nr_swap--;
> >> - free_swap_and_cache(entry);
> >> - pte_clear_not_present_full(mm, addr, pte, tlb->fullmm);
> >
> > Nitpick: IMHO you don't need to invert non_swap_entry() then it'll generate
> > a smaller diff, just add the new code above "continue".
>
> I tried this way, but that lead to long line splitting, so I rewrote the code like this.
> If you prefer to just add the new code above "continue", I will do it in the next version.
No worry then, feel free to keep it as is.
>
> >
> >> + if (!non_swap_entry(entry)) {
> >> + nr_swap--;
> >> + free_swap_and_cache(entry);
> >> + pte_clear_not_present_full(mm, addr, pte, tlb->fullmm);
> >> + } else if (is_hwpoison_entry(entry) ||
> >> + is_swapin_error_entry(entry)) {
> >> + pte_clear_not_present_full(mm, addr, pte, tlb->fullmm);
> >
> > Since it's been discussed and you're reposting a new version anyway, why
> > not start with either reusing hwpoison or pte markers? Or do you think it
> > should be for future to drop the new swap entry again?
> >
>
> IMHO if reusing hwpoison markers, there are some places that we need to distinguish them and do
> different processing (and maybe also well comment them) which will make code more complicated and
> somewhat hard to follow. And the "swapin error marker" here is most straightforward. And If pte markers
> will support the "swapin error case" in the future, I think it's fine to change to use it then.
> Does this make sense for you?
Yeah it's fine. If the pte marker things can finally land as expected,
maybe I can try it out as the 2nd user of it. :)
--
Peter Xu
